Application of CDMA in comparison to GSM

[rojos17]

Re: CDMA versus GSM..

Even though technically CDMA has better security in the radio link (spread spectrum), GSM also has advanced security algorithms in the radio link.
All in all, even when CDMA is a better technology, I think that the open of standard of GSM help the vendors make better solutions. For instance, in a GSM/GPRS network you can have modules from different vendor.

 

[daviddlc]

Re: CDMA versus GSM..

CDMA

- More bandwith
- More users
- More security
- Better audio quality
- More battery life

Both, the new technology coming is WCDMA.

WideBand CDMA.

 

[leoren_tm]

Re: CDMA versus GSM..

i WCDM combined gsm with cdma?

 

[saubhik]

Re: CDMA versus GSM..


CDMA


it is code division multiple access technique where it uses different code for encryption of data for different subscribers .
it is costlier.
it uses wider bandwidth .
it is reliable in message delivery or prooper line setup.
basically a cdma receiver is only a RAKE RECEIVER where it receives low amplitude signals and then after filtering the higher amplitude data signals from lower amplitude noise and then again amplifies the signal .
has the disadvantage that if a subscriber wants to change the service provider then he needs to change the set of mobile itselfas thwe whole RAKE RECEIVER should have to be changed (updation is happening in this point).



GSM


it is global system for Mobile Communication .
it uses lesser bandwidth wrt CDMA .
reliability of handsOff is respectively lower than CDMA .
cheaper in cost .
has the advantage that if a subscriber wants to change service provider he only needs to change the SIM of the mobile .

 

[pravin_dwaramwar]

Re: CDMA versus GSM..

As you know the mobile personal communicationsystems uses microwave frequencies above 800MHz for their transmission and reception purposes. They all are operating in some predefined or pre allocated frequency bands according to the international standards.

For operating in these microwave frequencies they all need some access methods. And these methods are:

1. Frequency division multiple access (FDMA)
2.Time division multiple access (TDMA)
3.Code division multiple access (CDMA)

Thus CDMA is one access technology which cell phones uses to transmit and receive data. You can understand the meaning of FDMA, TDMA and CDMA eazily by just noting the word meaning for ezch letter. That is FDMA puts each call on a separate frequency and TDMA assigns each call a certain portion of time on a designated frequency for the above mentioned purpose. But CDMA gives a unique code to each call and spreads it over the available frequencies. All these are multiple access systems because more than one user can use the specified CELL ( not cell phone!) at a time.

But GSM or Global System for Mobile uses the above mentioned TDMA ( Time Division Multiple Access ) for mobile communication purposes ! In other words GSM is a global standard based on TDMA and a very popular one in the entire Europe, Middle East, Asia and Africa and not an access code as CDMA but one global standard.( Remember it always....CDMA vs GSM is really misleading! it is CDMA vs TDMA..!)

GSM operates in the 900 MHz band (890 MHz - 960 MHz) in Europe and Asia and in the 1900 MHz band in the United States. Besides these facts we must know the limitations and advantages of each systems in a brief way. All these facts are highly technical but i will try my best to write the details suite for all the mouthshut readers.

First TDMA of GSM.
The data transmission in TDMA is actually not continuous. It occurs in bursts. But the time between these bursts for a single mobile phone user is very very short, so that he never knows that the speech of the other person is discontinuous!

As TDMA uses different time slots for transmission and reception your handset never need a duplexer. But it simply need a switch to transfer between transmission and reception sesseions!

But the CDMA system has a soft capacity limit. That is increasing the number of users will decreases the system performance.( any comments Reliance users..?..!!).
Channel data rates are very high in CDMA systems. But sel-jamming is a major problem.

AND NOW SOME INTERESTING FACTS

Above are the technical facts you must know. But as you are very familiar with GSM of BSNL, AIRTEL, ESCOTEL etc. and the CDMA of Relience i know you are also eager to know about some commonly misunderstood things.

GSM is a widely spread standard and CDMA is a patented technology. That is you must pay a royalty for using CDMA! Also GSM covers the entire Europe , Asia except Korea, Africa and Middle East. So being a GSM user you have virtually an international roaming. You can eazily use a GSM phone in any of these countries while roaming.

GSM users are almost 8 times in number than CDMA users worldwide. By being a GSM user you will be part of the largest mibile community.
And coming to voice quality GSM is far better than CDMA, as i mentioned it earlier. CDMA base stations consumes less power than GSM and also covers a large distance. That is the cell size in CDMA is larger compared to GSM.

In general i say both GSM and CDMA are frontier technologies and both have good and bad qualities. And in the case of mobile handsets the fact is that GSM handsets are very popular and many of the new facilties are readily available in GSM phones with lesser price. The reason is simple...nokia and motorola needs profit...and they will invest more in GSM because GSM has 8 times more users than CDMA.

In the case of data rates also GSM is nowadays improving with their new GPRS. With GPRS it is expected that a data rate of about 171 kbps may be provided however on a shared basis between multiple users. GPRS enables an existing GSM system to communicate with any application or network that uses packet switching. GPRS thus allows subscribers to connect to the Internet to access applications as web browsing, mail and FTP.

 

[si14]

Re: CDMA versus GSM..

CDMA stands for "Code Division Multiplex Access".
The GSM generations are:
TDMA(time division)
FDMA (frequency division)
and the 3rd one is CDMS,
But I heared there is going to be another technology like OFDM in near future.

 

[eehero]

CDMA versus GSM..

ok i begginer with digital communication, CDMA and WIMAX what is about it?

 

[lordsathish]

Re: CDMA versus GSM..

CDMA is based on the concept of spread spectrum... i.e increasing the bandwidth of the signal by multiplying the signal by a high frequency code... so that the signal can be recovered at th receiver only by multiplying the signal again by the code word... if the code words are orthogonal then multiplying the signal with the wrong code at the receiver will not give the transmitted signal... hence each user can be given a different code that he uses... so that all the users use the same bandwidth...

 

[jaya000]

Re: CDMA versus GSM..

Interesting topic & nice replies. Very informative.

 

[lordsathish]

Re: CDMA versus GSM..

yes... its interesting... does any one know how do they generate such code words that are orthogonal...